The present invention relates to an image forming system including a printer or a copy machine which forms images on a recording medium such as paper.
In the past, an image forming system including a printer or a copy machine was developed which sequentially printed images on a recording medium (hereinafter referred to as a recording sheet) such as paper or an OHP (over head projector) sheet. Sequential page numbers were printed on each recording sheet.
In the case that four sheets of documents shown in FIG. 6(a) are copied, in a single sided print mode as shown in FIG. 6(b), page numbers “-1-” to “-4-” are printed on single sides of four recording sheets, while in a double sided printing mode as shown in FIG. 6(c), sequential page numbers “-1-” to “-4-” are printed on double sides of two recording sheets.
Recently, technology relating to an image forming apparatus which can print not only an image but also the page number is disclosed in Patent Document 1. Further Patent Document 1 discloses the technology relating to an image forming apparatus in which an operator can reserve whether the page number is printed or not.
[Patent Document 1] Japanese Tokkai 2001-347735
However, in the case of counting page numbers in Patent Document 1, an insertion sheet is considered to be a printed sheet same as a recording sheet, and thereby page number counting is conducted not only for recording sheets but also for inserted sheets. That is, a page number is printed on the inserted sheet, or skipped for the inserted sheet, depending upon whether an image, which includes a blank image and its page number, is to be printed on the inserted sheet, and depending upon whether a page number is to be counted for each page.
Further, in the case of double sided printing, when the page number is not printed on the inserted sheet, necessary is a message saying that page numbers are omitted on front and back, which is very cumbersome, and requires a complicated control.
Additionally, in the above control, an inserted sheet which does not pass through the image forming apparatus is usually a sheet on which an image is not printed. Accordingly, when a sheet has not passed through the image forming apparatus, the management and control of an assigned page number have not been conducted, and therefore there is no assigned page numbers for every sheet which has not passed through the image forming apparatus. This results in a problem in that page numbering on every page including the inserted sheets is not controlled.
That is, in an image forming system featuring a function wherein the recording sheets which have not passed through the image forming apparatus are inserted at a predetermined position between plural recording sheets which have passed through the image forming apparatus, it is very problematic to correctly print the sequential page numbers on all the ejected recording sheets, in the ejected order.
For example, when four sheets of documents shown in FIG. 6(a) are copied by a conventional image forming apparatus, in a single sided print mode, the page number is not printed on the recording sheet inserted in the third order as shown in FIG. 7(a), and further, in a double sided printing mode, the page numbers are not printed on the recording sheet inserted in the second order as shown in FIG. 7(b). Therefore, page numbering not only on the recording sheet but also on the insertion sheet are not controlled, resulting in a problem.